Torsional Force Transmitting Apparatus

ABSTRACT

The present invention aims to couple a propeller with a power output shaft to transmit the torsional force of the power output shaft to the propeller. The apparatus includes a first sleeve and a second sleeve that form a coupling surface between them to hold a torsional force transfer means. The torsional force transfer means is coupled with the first sleeve and the second sleeve to transmit only a selected amount of the torsional force. The first sleeve has a first outer surface and the second sleeve has a second inner surface that are engaged respectively with the propeller and the power output shaft in the rotating direction so that the power output shaft can transmit the torsional force to the propeller. In the event that the propeller is overloaded the torsional force transfer means between the first sleeve and the second sleeve slip to form a protection mechanism.

FIELD OF THE INVENTION

The present invention relates to a torsional force transmittingmechanism and particularly to a torsional force transmitting apparatusfor propellers to provide overload protection.

BACKGROUND OF THE INVENTION

A torsional force transmitting apparatus aims to couple a propeller witha power output shaft. When a boat sails the propeller might hit unknownobjects such as reefs. Such an incident could generate an excessive loadtorsional force and result in breaking or damage of the propeller,engine and gear box. To protect the propeller, engine and gear box, thetorsional force transmitting apparatus ought to be slipping or broken.By replacing the torsional force transmitting apparatus with a new onethe boat can sail again. Such an approach can save repair cost and time.

However, the conventional torsional force transmitting apparatus used ona propeller is formed by squeezing a round rubber into a round innerhole of the propeller through a press. By controlling the compressedamount of the rubber a positive force to the round inner hole of thepropeller is provided. And by controlling the amount of the positiveforce the amount of torsional force that can be transmitted by therotating propeller can be determined. In the event of overloading, andslipping or breaking occurs, a protection mechanism is formed. But suchan approach has to rely on the press to perform replacement and repairswhen damage occurs. And the replacement and repairs have to be done at aprofessional repair shop. Moreover, the positive force provided by therubber highly depends on temperature. Used on a high horsepower engine,the temperature rises easily and the rubber becomes soft and results inslipping. At a lower temperature the rubber becomes harder, theprotection effect diminishes.

U.S. Pat. No. 4,566,855 discloses another torsional force transmissionapparatus for propellers. It has a rubber-made resilient shock mountsleeve with the outer perimeter formed in a gear shape to mate an innerhole of a propeller and an inner hole formed in another gear shape tomate the outer perimeter of a spline driver sleeve adaptor. Bycontrolling the depth of the gear, a positive force is generated bydeformation of the rubber when the resilient shock mount sleeve rotatesthat is used to transmit the torsional force. Namely the depth of thegear can determine the amount of a load torsional force, thereby controlthe transmitting torsional force to produce slipping. Such a techniquedoes not do installation by compaction, hence does not require a pressto do replacement when damage occurs. Users can do repairs by themselvesif desired. But due to the rubber is installed without being compressedin advance, and only the teeth of the gear are compressed duringrotation, the compressed amount is little. Hence the transmittingtorsional force also is limited. It is not suitable for a high powerengine system.

U.S. Pat. No. 5,322,416 discloses yet another technique which has theresilient shock mount sleeve made from plastics. The outer perimeter ofthe resilient shock mount sleeve and the inner hole of the propeller areformed respectively in an octagonal shape. The resilient shock mountsleeve has an inner hole and the drive sleeve has an outer perimeterthat are formed respectively in a gear shape. The resilient shock mountsleeve generates a positive force resulting from deformation duringrotation to transmit the torsional force. It also is not installed bycompaction and can be repaired by the users. As the material is switchedto plastics, a smaller compression amount can transmit a greatertorsional force. Hence it can be used on a higher power engine system.In the event that impact of an external force occurs that exceeds thetorsional load, the plastics fracture to provide a protection mechanism.But the plastics still highly depend on temperature. Use in anenvironment of a lower temperature, it is hardened and might not breakeven under the impact of an estimated breakable torsional force. As aresult, damages of the propeller, engine and gear box could occur.Moreover, when the rotational direction of the propeller is switched thecontact surface of the resilient shock mount sleeve and the propelleralso changes. During switching a great deal of noise and shock aregenerated due to no buffer is provided.

SUMMARY OF THE INVENTION

Therefore the primary object of the present invention is to provide atorsional force transmitting apparatus that is not easily affected bytemperature and generates less noise and shock.

The torsional force transmitting apparatus of the invention aims to beused on propellers to couple a propeller with a power output shaft totransmit the torsional force of the power output shaft to the propeller.It includes a first sleeve, a second sleeve and a torsional forcetransfer means. The first sleeve has a first inner surface which iscoupled with a second outer surface of the second sleeve in a rotarymanner to form a coupling surface. The torsional force transfer means islocated on the coupling surface. The torsional force transfer meansconnects the first sleeve and the second sleeve, and can transmit only aselected amount of the torsional force. The first sleeve has a firstouter surface and the second sleeve has a second inner surface that areengaged respectively with the propeller and the power output shaft inthe rotating direction.

By means of the construction set forth above, the selected amount oftorsional force transmittable can be controlled through the torsionalforce transfer means. When the torsional force of the power output shaftis transmitted to the propeller, and the propeller hits a unknown objectand results in significant increase of the torsional force andoverloaded, the torsional force transfer means between the first sleeveand the second sleeve breaks and loosens, hence the first sleeve and thesecond sleeve rotate idly to provide protection for the propeller,engine and gear box.

The foregoing, as well as additional objects, features and advantages ofthe invention will be more readily apparent from the following detaileddescription, which proceeds with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of the invention.

FIG. 2 is a cross section of the invention in a use condition.

FIG. 3 is an exploded view of another embodiment of the invention.

FIG. 4 is a fragmentary cross section of yet another embodiment of theinvention.

FIG. 5 is a fragmentary cross section of still another embodiment of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Please refer to FIGS. 1 and 2, the torsional force transmittingapparatus according to the invention aims to transmit the torsionalforce of a power output shaft 10 to a propeller 20. It includes a firstsleeve 30A, a second sleeve 40A and a torsional force transfer means50A. The first sleeve 30A has a first inner surface 31 and a first outersurface 32 which is non-circular. The propeller 20 also is formed in anon-circular profile such that the second outer surface 32 can beengaged with the propeller 20 in the rotating direction.

The second sleeve 40A has a second inner surface 41 and a second outersurface 42. The second inner surface 41 has annular inner teeth 43formed thereon. The power output shaft 10 has annular outer teeth 11mating the annular inner teeth 43 so that they can be coupled andinstalled together with the second inner surface 41 engaging with on thepower output shaft 10 in the rotational direction. The power outputshaft 10, through the mutual engagement of the annular inner teeth 43and the annular outer teeth 11, can transmit the torsional force to thesecond sleeve 40A.

The first inner surface 31 of the first sleeve 30A and the second outersurface 42 of the second sleeve 40A are coupled together in a rotarymanner to form a coupling surface 35. The torsional force transfer means50A is located on the coupling surface 35 by disposing an adhesive 36onto the coupling surface 35. By changing the type and size of thebonding surface of the adhesive 36 the amount of the torsional forcetransmittable can be controlled. Hence the torsional force transfermeans 50A which couples the first sleeve 30A and the second sleeve 40Acan transmit only a selected amount of the torsional force.

By means of the construction set forth above, when the power outputshaft 10 is engaged with the propeller 20, and the propeller 20 hits anunknown object and results in great increase of the torsional force andoverloaded, the torsional force transfer means 50A breaks down so thatthe first sleeve 30A and the second sleeve 40A rotate idly. As a resultbreaking of the propeller 20 can be prevented. And the engine and gearbox also are protected.

Refer to FIG. 3 for another embodiment of the invention. It has atorsional force transfer means 50B located on the coupling surface 35between the first inner surface 31 of a first sleeve 30B and the secondouter surface 42 of a second sleeve 40B. The coupling surface 35 has atleast one flute 44 formed thereon to hold an elastic element 45. Theflute 44 is evenly spaced on the coupling surface 35. The elasticelement 45 includes a rubber strut 451 coupling with a spring 452. Thesecond sleeve 40B has two ends holding respectively a first pad 46 and asecond pad 47. The first sleeve 30B runs through the second sleeve 40B.After the elastic element 45 is wedged in the flute 44, the upper pad 46and the lower pad 47 are bonded to the first sleeve 30B, thereby toprevent the first sleeve 30B and the second sleeve 40B from slidingagainst each other and anchor the elastic element 45. In the event thatthe torsional force between the first sleeve 30B and the second sleeve40B is excessive, the elastic element 45 is compressed and deforms, andan idle rotation occurs between the first sleeve 30B and the secondsleeve 40B. By changing the number of the flute 44, the torsional forcetransmittable can be controlled. The upper pad 46 and the lower pad 47may be made from rubber. The upper pad 46 and the lower pad 47 areformed at a dimension slightly larger than the inner diameter of thepropeller 20. Hence when the first sleeve 30B is engaged with thepropeller 20 through the upper pad 46 and the lower pad 47 in therotational direction a shock absorbing effect can be achieved to reducenoise and vibration during rotation of the propeller 20.

Refer to FIG. 4 for yet another embodiment of the invention. The secondouter surface 32 of a first sleeve 30C is encased by an elastic material60 which may be rubber or plastics. The first sleeve 30C and thepropeller 20 are engaged through the elastic material 60. Such astructure also can absorb shock to reduce noise and shock duringrotation of the propeller 20.

Refer to FIG. 5 for still another embodiment of the invention. Thesecond outer surface 32 of a first sleeve 30D has a plurality of ribs321. The inner hole of the propeller 20 has a corresponding shape.Moreover, there are a plurality of elastic struts 70 on one side of theribs 321 to be interposed between the propeller 20 and the first sleeve30D. The first sleeve 30D is in contact with the propeller 20 throughthe elastic struts 70. Therefore a shock absorbing effect can beachieved to reduce noise and shock during rotation of the propeller 20.

As a conclusion, the present invention provides torsional force transfermeans 50A and 50B between the first sleeves 30A and 30B and secondsleeves 40A and 40B. The torsional force transfer means 50A and 50B cantransmit only a selected amount of torsional force, thus form aprotection mechanism. Thereby it can protect the more expensivepropeller 20 or the engine and gear box coupling with the power outputshaft 10. By selecting varying types and bonding sizes of the adhesive36 or changing the number of the flute 44, the transmittable torsionalforce can be controlled to suit different types of propeller 20. In theevent of damage, due to the first sleeves 30A and 30B, the secondsleeves 40A and 40B, and the propeller 20 are not engaged by compactionin the axial direction, replacement can be done easily to meet user'srequirements.

1. A torsional force transmitting apparatus to transmit a torsionalforce of a power output shaft to a propeller, comprising: a first sleevewhich has a first inner surface and a first outer surface which isengaged with the propeller in a rotational direction; a second sleevewhich has a second inner surface and a second outer surface, the secondinner surface being engaged with the power output shaft in therotational direction, the first inner surface and the second outersurface being coupled together in a rotary manner to form a couplingsurface; and a torsional force transfer means located on the couplingsurface to couple the first sleeve and the second sleeve and transmitonly a selected amount of the torsional force.
 2. The torsional forcetransmitting apparatus of claim 1, wherein the torsional force transfermeans is formed by disposing an adhesive on the coupling surface; theamount of the torsional force transmittable being controlled by changingthe type and bonding size of the adhesive.
 3. The torsional forcetransmitting apparatus of claim 1, wherein the torsional force transfermeans is formed by carving at least one flute on the coupling surfacebetween the first inner surface and the second outer surface to allow anelastic element to be wedged in, the second sleeve having two ends tohold respectively a upper pad and a lower pad that are bonded to thefirst sleeve to prevent the first sleeve and the second sleeve fromsliding against each other to anchor the elastic element, the amount ofthe torsional force transmittable being controlled by changing thenumber of the flute.
 4. The torsional force transmitting apparatus ofclaim 3, wherein the elastic element includes a rubber strut couplingwith a spring.
 5. The torsional force transmitting apparatus of claim 3,wherein the upper pad and the lower pad are made from rubber, and formedat a dimension slightly larger than an inner diameter of the propeller.6. The torsional force transmitting apparatus of claim 1, wherein thefirst outer surface of the first sleeve is encased by an elasticmaterial.
 7. The torsional force transmitting apparatus of claim 6,wherein the elastic material is rubber.
 8. The torsional transmissionapparatus of claim 6, wherein the elastic material is plastics.
 9. Thetorsional force transmitting apparatus of claim 1, wherein the firstouter surface is non-circular and the propeller has a correspondingnon-circular profile.
 10. The torsional force transmitting apparatus ofclaim 1, wherein the second inner surface has annular inner teeth andthe power output shaft has annular outer teeth corresponding to theannular inner teeth to be coupled together for installation such thatthe annular inner teeth and the annular outer teeth are engaged to allowthe power output shaft to transmit the torsional force to the secondsleeve.
 11. The torsional force transmitting apparatus of claim 1,wherein the first outer surface has a plurality of ribs and thepropeller has an inner hole formed in a shape corresponding to the firstouter surface, the propeller and the first sleeve being interposed by aplurality of elastic struts on one side of the ribs.